This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-109541, filed Apr. 11, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to a keyboard unit having pop-up key-tops and an electronic apparatus incorporating the keyboard unit.
Recently, in the market involving portable computers, there is a demand for forming the portable computers thinner and more compact to facilitate to carry them. To satisfy the demand, it is an urgent necessity to make thin main components such as a main body having a keyboard unit, a liquid crystal display unit, etc.
A keyboard unit incorporated in the main body of a portable computer has a number of key-tops to be operated by the fingers of the operator. Each of the key-tops is vertically movably supported by a key-top support mechanism of a pantograph type located on a keyboard base. The key-top support mechanism has a pair of link levers. These link levers are assembled into an X-shaped structure, and connected so that they can pivot relative to each other. A sheet switch is provided on the keyboard base. This switch has a number of movable contacts and a number of stationary contacts. The movable contacts are opposed to the stationary contacts below the key-tops.
In a keyboard unit of this type, to realize comfortable input operability, it is necessary, when a finger has pushed a key-top, to enable the operator to clearly feel a click. To this end, the conventional keyboard unit incorporate an elastically deformable pressing member interposed between each key-top and the switch. This pressing member is formed of a flexible rubber material such as silicone rubber, and is cup- or dome-shaped such that it opens to the switch. Each pressing member always upwardly presses a corresponding key-top away from the switch. Upper portions of the pressing members form projections for pressing the respective movable contacts of the switch.
Accordingly, when a finger pushes a key-top, a corresponding pressing member is depressed to thereby cause the finger to feel a click, and the projection of the pressing member presses a corresponding movable contact of the switch. As a result, the movable contact is brought into contact with a corresponding stationary contact, thereby closing the switch. The keyboard unit, in turn, outputs an input signal indicating that a desired key-top has been pushed.
In a keyboard unit for a portable computer, it is necessary to secure the stroke amount of each key-top so as to cause the operator to clearly feel that each key-top has been pushed. However, the stroke amount of each key-top significantly influences the thickness of the keyboard unit. The larger the stroke amount, the thicker the keyboard unit. The increase of the stroke amount is a hindrance to the thinning of the computer.
A so-called pop-up keyboard unit is known as an improvement developed in light of the above. In this improvement, key-tops are depressed and superposed on the switch when the computer is not used, and are protruded upwardly only when the computer is used.
For example, Japanese Patent Application KOKAI Publication No. 8-54964 discloses an example of the pop-up keyboard unit. In this keyboard unit, cup- or dome-shaped pressing members are provided on the upper surface of the switch. The switch is supported on a keyboard base so that it can slide between a first position in which the pressing members are positioned below key-top support mechanisms, and a second position in which the pressing members are displaced from the key-top support mechanisms. While the liquid display unit is open, the switch is urged by a spring to the first position. When the liquid display unit is closed, the switch is forcibly slid from the first position to the second position.
When the switch is slid to the first position, the pressing members raise the key-top support mechanisms. Accordingly, the link levers of each key-top support mechanism upwardly pivot on portions thereof connected to the keyboard base, whereby the key-tops are kept in a position in which they are upwardly protruded above the switch by a desired amount.
When, on the other hand, the switch is slid to the second position, the pressing members are displaced from the key-top support mechanisms. Accordingly, the raise of the key-top support mechanisms by the pressing members is released. As a result, the link levers of each key-top support mechanism downwardly pivot on portions thereof connected to the keyboard base, whereby the key-tops are depressed. This structure enables thinning of the keyboard unit while securing the stroke amount of each key-top, which is necessary to depress it.
In the conventional keyboard unit, each pressing member for pressing a corresponding movable contact or causing the operator to feel a click, when a finger pushes a corresponding key-top, is a component separate from the key-top support mechanism. Therefore, the number of components incorporated in the keyboard unit is inevitably large, which results in high cost. Further, since it is necessary to provide the same number of pressing members as the key-tops on the switch, a lot of time and effort are required, which degrades the efficiency of assembly of the keyboard unit.
As an improvement for overcoming this, a keyboard unit is known, in which the link levers of a key-top support mechanism are formed of pressed component parts, and an elastically deformable tongue member for pressing a switch is formed integral with one of the link levers. In this case, the tongue member directly presses the switch when the link levers of the key-top are downwardly pivoted in accordance with the push operation of the key-top. This structure does not require the above-described pressing members of rubber, which results in cost reduction.
However, the tongue member formed of a metal plate has a higher rate of spring than the rubber pressing member, and hence has a strong spring force which causes the tongue member to try to maintain its initial state against a force occurring when the tongue member is brought into contact with the switch. This being so, the operator feels heavy touch when pushing a key-top. In other words, the input operability is degraded.
Furthermore, since the tongue member is formed integral with the link lever by press working, it is necessary to remake a mold for press working in order to change the rate of spring of the tongue member. Thus, it is difficult to change the rate of spring of the tongue member for improving the key touch obtained when pushing each key-top.
In addition, in the conventional pop-up keyboard unit, the flexible rubber pressing member is brought into contact with the key-top support mechanism each time the liquid crystal display unit is opened or closed. Accordingly, it is possible that the pressing member will be degraded or worn out in an early stage.
Also, the rubber pressing member generates a strong frictional force in a portion thereof connected to the key-top support mechanism. Accordingly, high resistance occurs when sliding the switch, with the result that each key-top cannot smoothly be raised or depressed.
It is a first object of the invention to provide a keyboard unit and electronic apparatus of excellent operability, which enable the operator to have nice feeling when pushing each key-top, although they incorporate a structure in which pressing members made of a metal are arranged to press the respective movable contacts of a switch.
It is a second object of the invention to provide a keyboard unit and electronic apparatus of excellent operability, which can easily raise and depress each key-top with a small force of the operator while causing the operator to have nice feeling when they push each key-top.
To attain the first object, there is provided a keyboard unit according to a first aspect. This keyboard unit comprises: a keyboard base; a number of key-tops arranged above the keyboard base; a switch in the form of a sheet interposed between the keyboard base and the key-tops, the switch having a number of movable contacts arranged corresponding to the key-tops, and a number of stationary contacts opposed to the respective movable contacts; and a number of key-top support mechanisms located on the keyboard base and supporting the respective key-tops such that the key-tops can move vertically.
Each of the key-top support mechanisms includes first and second link levers pivotably connected to each other, the first and second link levers supporting each of the key-tops and being pivoted when the each key-top is pushed down, the first link lever being made of a metal and having an elastically deformable pressing section that is formed integral therewith as one body. A number of elastically deformable load receiving sections are interposed between the respective pressing sections of the first link levers and the respective movable contacts of the switch.
Further, to attain the first object, there is provided an electronic apparatus according to a second aspect. This electronic apparatus comprises a box-shaped main body; and a keyboard unit mounted on the main body. The keyboard unit includes: a keyboard base; a number of key-tops arranged above the keyboard base; a switch in the form of a sheet interposed between the keyboard base and the key-tops, the switch having a number of movable contacts arranged corresponding to the key-tops, and a number of stationary contacts opposed to the respective movable contacts; a number of key-top support mechanisms located on the keyboard base and supporting the respective key-tops such that the key-tops can move vertically, each of the key-top support mechanisms including first and second link levers pivotably connected to each other, the first and second link levers supporting each of the key-tops and being pivoted when the each key-top is pushed down, the first link lever being made of a metal and having an elastically deformable pressing section that is formed integral therewith as one body; and a number of elastically deformable load receiving sections interposed between the respective pressing sections of the first link levers and the respective movable contacts of the switch.
In each of the above-described structures, in a free state in which no key-top is pushed down, the pressing sections of the first link levers touch the load receiving sections of the switch. In other words, the first and second link levers are in a position remote from the switch, thereby raising the key-tops to their stand-by positions in which they protrude above the switch.
When a finger pushes down one of the key-tops, the first and second link levers of the one key-top downwardly pivot toward the switch. As a result of this pivoting, the pressing section of the first link lever is pressed against a corresponding load receiving section and hence elastically deformed. Accordingly, the force applied to the key-top to push it down is transmitted from the pressing section to a corresponding movable contact of the switch via the load receiving section. This movable contact is brought into contact with a corresponding stationary contact, whereby the switch is closed.
In the above structures, an elastically deformable load receiving section is interposed between the pressing section of each first link lever and the switch. Therefore, even if the rate of spring of the pressing section is made lower than in the prior art in order to make it easier to warp the pressing section, the elasticity of the load receiving section compensates the reduced spring rate of the pressing section. Therefore, although the pressing sections are formed of a metal, the key-tops can be pushed down with a small force, and clear click feeling can be obtained when the load receiving section deforms. Accordingly, the operator can obtain clear and comfortable feeling of pushing down each key-top. Thus, a comfortable input operation can be realized.
Further, the change of the elasticity of the load receiving section can vary the load characteristic obtained when each key-top is pushed down. Accordingly, it is not necessary to change the shape of the pressing section formed integral with the first link lever. Therefore, where the first link lever having the pressing section is formed by plate press working, the load characteristic can be easily changed without remaking a mold for press working.
To attain the second object, there is provided a keyboard unit according to a third aspect. This unit comprises: a keyboard base; a number of key-tops arranged above the keyboard base; a switch in the form of a sheet interposed between the keyboard base and the key-tops, the switch having a number of movable contacts arranged corresponding to the key-tops, and a number of stationary contacts opposed to the respective movable contacts; a number of key-top support mechanisms located on the keyboard base and supporting the respective key-tops such that the key-tops can move vertically.
Each of the key-top support mechanisms includes first and second link levers pivotably connected to each other, the first and second link levers supporting each of the key-tops and being pivoted when the each key-top is pushed down, the first link lever being made of a metal and having an elastically deformable pressing section that is formed integral therewith as one body. A movable sheet is interposed between the switch and the pressing sections of the first link levers, the movable sheet having a number of elastically deformable projections made of a metal, and being movable between a first position in which the projections are aligned with the respective pressing sections, and a second position in which the projections are not aligned with the pressing sections, the projections being brought into contact with the respective pressing sections when the movable sheet is in the first position.
To attain the second object, there is provided an electronic apparatus according to a fourth aspect. This apparatus comprises: a box-shaped main body; a keyboard unit mounted on the main body; and a lid supported by the main body such that it can pivot between a closed position in which it is folded on the keyboard unit from above, and an open position in which it stands behind the keyboard unit.
The keyboard unit includes: a keyboard base; a number of key-tops arranged above the keyboard base; a switch in the form of a sheet interposed between the keyboard base and the key-tops, the switch having a number of movable contacts arranged corresponding to the key-tops, and a number of stationary contacts opposed to the respective movable contacts; a number of key-top support mechanisms located on the keyboard base and supporting the respective key-tops such that the key-tops can move vertically, each of the key-top support mechanisms including first and second link levers pivotably connected to each other, the first and second link levers supporting each of the key-tops and being pivoted when the each key-top is pushed down, the first link lever being made of a metal and having an elastically deformable pressing section that is formed integral therewith as one body; and a movable sheet interposed between the switch and the pressing sections of the first link levers, the movable sheet having a number of elastically deformable projections made of a metal, and being movable between a first position in which the projections are aligned with the respective pressing sections, and a second position in which the projections are not aligned with the pressing sections, the projections being brought into contact with the respective pressing sections when the movable sheet is in the first position.
In each of the above-described structures, when the movable sheet is in the first position, projections provided thereon touch the respective pressing sections. In other words, the first and second link levers are in a position remote from the switch, thereby raising the key-tops to their stand-by positions in which they protrude above the switch.
When a finger pushes down one of the key-tops, the first and second link levers of the one key-top downwardly pivot toward the switch. As a result of this pivoting, the pressing section of the first link lever is pressed against a corresponding load receiving section and hence elastically deformed. Accordingly, the force applied to the key-top to push it down is transmitted from the pressing section to a corresponding movable contact of the switch via the load receiving section. This movable contact is brought into contact with a corresponding stationary contact, whereby the switch is closed.
When the movable sheet is shifted from the first position to the second position, the projections thereon are out of contact with the pressing sections. As a result, the first and second link levers downwardly pivot toward the switch due to their own weights, and are depressed. Thus, the key-tops are lowered to the switch, which means that the thickness of the keyboard unit is reduced.
In the above structures, an elastically deformable projection is interposed between the pressing section of each first link lever and the switch. Therefore, even if the rate of spring of the pressing section is made lower than in the prior art in order to make it easier to warp the pressing section, the projection compensates the reduced spring rate of the pressing section. Therefore, although the pressing sections are formed of a metal, the key-tops can be pushed down with a small force, and clear click feeling can be obtained when the projection deforms.
Further, since the pressing section of each first link lever and a corresponding projection of the movable sheet to be brought into contact with the pressing section are formed of a metal, a significant frictional force will not occur therebetween. This prevents each projection from being worn or damaged, and also prevents a great resistance from occurring when the movable sheet is slid. As a result, vertical motion of each key-top can be executed smoothly.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.